This invention relates to molding apparatus and plastic injection molding methods of producing plastic members incorporating an O-ring retainer and further including products incorporating filtration material molded therein.
There are many applications requiring a molded component to retain an O-ring. In these applications, it is often desirable to provide a groove in a component for receipt of an O-ring that provides a high quality seal at the juncture between the O-ring, the component, and the part which the O-ring encircles, such as a shaft or the like. However, this desirable O-ring feature has been compromised with the need for plastic components that can be manufactured efficiently and cost effectively. For example, in one prior art application requiring a clean hydraulic fluid about a shaft, a plastic member comprising concentric annular ribs with filtration material therebetween was used, with the effective seal between the shaft and the member relying upon a friction fit between an annular rib with filtration material and the shaft. Obviously, such a component is not as effective as an O-ring incorporated therein, which provides a high quality seal with the shaft.
In the manufacturing of plastic parts with interior placed O-rings, grooves on the interior diameter of a part may be made with collapsing cores. Examples of such an apparatus and method to produce such grooves are disclosed in U.S. Pat. Nos. 3,966,385 and 4,044,092. Without detailing their construction herein, suffice it to say that these molds are expensive, complicated, and difficult to maintain due to the complexity of their numerous moving parts that must be actuated during each operating cycle to obtain the desired groove in the resulting plastic parts. Further, they are generally limited in depth of groove creation due to internal geometries of the molding apparatus. Such a method and apparatus, although possible, may not be commercially practicable as to cost effectiveness of the method, resulting component and maintenance of the mold.
Instead of collapsing cores, it is conceivable that an O-ring groove is formed using conventional mold halves to produce two components, each forming only half the groove each, with the components then glued, cemented, melted, or the like together. Such a method is obviously uneconomical and could lead to a less than acceptable O-ring seal due to the multiplicity of parts and the like.
Alternatively, it may be possible to manufacture such a component by placing an O-ring into a two piece mold and molding a component about such an O-ring. However, such an in situ method requires particular component materials and complex interactions between the O-ring material and the overmolded portions of the molded product. Obviously, such a mold and method would involve complex and costly manufacturing apparatus and processes. Further, the resulting product may have inherent structural and material limitations.